Effects of subgrains on critical current properties in melt-processed RE–Ba–Cu–O bulksuperconductors

Abstract

We have studied the microstructures of subgrains in large single-domain RE–Ba–Cu–Obulk superconductors and their effects on superconducting properties. Subgrains with highmisorientation angles were seen at the positions of the later stage of melt growth, orthe positions where the second-phase particles are large in size and volume. Anelectron backscattering diffraction technique revealed that the orientation of thesecond-phase particles affects the orientation of the matrix phase, some of whichforms the subgrain boundaries. Electric and magnetic measurements have beenperformed for several samples having different subgrain geometries and the results ofI–V and resistivity measurements indicated that subgrains act as weak links, especially in ahigh magnetic field region.